let _Vue = null
function cleanPath (path) {
  return path.replace(/\/\//g, '/')
}
function getCurrentPath () {
  var href = window.location.href
  var index = href.indexOf('#')
  if (index < 0) {
    return ''
  }

  href = href.slice(index + 1)

  var searchIndex = href.indexOf('?')
  if (searchIndex < 0) {
    var hashIndex = href.indexOf('#')
    if (hashIndex > -1) {
      href = decodeURI(href.slice(0, hashIndex)) + href.slice(hashIndex)
    } else { href = decodeURI(href) }
  } else {
    href = decodeURI(href.slice(0, searchIndex)) + href.slice(searchIndex)
  }

  return href
}
export default class VueRouter {
  static install (Vue) {
    // 1 判断当前插件是否被安装
    if (VueRouter.install.installed) {
      return
    }
    VueRouter.install.installed = true
    // 2 把Vue的构造函数记录在全局
    _Vue = Vue
    // 3 把创建Vue的实例传入的router对象注入到Vue实例
    // _Vue.prototype.$router = this.$options.router
    _Vue.mixin({
      beforeCreate () {
        if (this.$options.router) {
          _Vue.prototype.$router = this.$options.router
        }
      }
    })
  }

  constructor (options) {
    this.options = options
    this.routeMap = {}
    // observable
    this.data = _Vue.observable({
      current: getCurrentPath()
    })
    this.init()
  }

  init () {
    this.createRouteMap()
    this.initComponent(_Vue)
    this.initEvent()
  }

  createRouteMap () {
    // 遍历所有的路由规则 吧路由规则解析成键值对的形式存储到routeMap中
    this.options.routes.forEach(route => {
      this.routeMap[route.path] = route.component
    })
  }

  initComponent (Vue) {
    Vue.component('router-link', {
      props: {
        to: String
      },
      render (h) {
        return h('a', {
          attrs: {
            href: this.to
          },
          on: {
            click: this.clickhander
          }
        }, [this.$slots.default])
      },
      methods: {
        clickhander (e) {
          const base = '/'
          history.pushState({}, '', this.to)
          window.location.replace(cleanPath(base + '/#' + this.to))
          e.preventDefault()
        }
      }
    })
    const self = this
    Vue.component('router-view', {
      render (h) {
        const cm = self.routeMap[self.data.current]
        return h(cm)
      }
    })
  }

  initEvent () {
    window.addEventListener('hashchange', () => {
      console.log(window.location.href)
      this.data.current = getCurrentPath()
    })
  }
}
